Total Ionizing Dose Effects on DRAM Data Retention Time (original) (raw)

Monitoring Methodology for TID Damaging of SDRAM Devices based on Retention Time Analysis

2004

Total ionizing dose (TID) is a potential problem for solid state devices exposed to ionizing radiation. An important parameter to define is the level of TID the device can tolerate. This value is very useful in order to predict its operative life time in a radiation environment. In this paper an online monitoring method to measure the degradation of synchronous dynamic RAM (SDRAM) commercial off the shelf (COTS) devices due to TID is proposed. The method is based on the measurement of the bit retention time, that is the time the information is retained in a memory cell without refresh. This approach is based on the observation that on same die, a dispersion of the devices' characteristics exists. So, the device degradation will appear in a more evident way in those memory cells having worst electrical characteristics. For this reason, there is a gradual increment of the number of memory cells that do not maintain their initialization value with the increment of the absorbed dose. The proposed method is useful to monitor the real level of degradation of a SDRAM device in order to optimize maintenance activity and graceful performance degradation techniques. SDRAM devices are used as a TID radiation defector to monitor the real dose absorbed by itself, and thus by the whole apparatus. The method is based on functional test that a SDRAM controller can easily perform on empty memory blocks without requiring dedicated hardware. This paper presents the experimental setup and the results of a preliminary TID test with a 60Co gamma ray source on SDRAM COTS to validate the method.

Radiation Induced Variable Retention Time in Dynamic Random Access Memories

IEEE Transactions on Nuclear Science, 2020

The effect of gamma-ray and neutron radiations on the Variable Retention Time (VRT) phenomenon occurring in Dynamic Random Access Memory (DRAM) is studied. It is shown that both ionizing radiation and non-ionizing radiation induce VRT behaviors in DRAM cells. It demonstrates that both Si/SiO2 interface states and silicon bulk defects can be a source of VRT. It is also highlighted that radiation induced VRT in DRAMs is very similar to radiation induced Dark Current Random Telegraph Signal (DC-RTS) in image sensors. Both phenomena probably share the same origin but high magnitude electric fields seem to play an important role in VRT only. Defect structural fluctuations (without change of charge state) seem to be the root cause of the observed VRT whereas processes involving trapping and emission of charge carriers are unlikely to be a source of VRT. VRT also appears to be the most probable cause of intermittent stuck bits in irradiated DRAMs.

Total Ionizing Dose Effects on Data Retention Capabilities of Battery-Backed CMOS SRAM

IEEE Transactions on Nuclear Science, 2000

Abstract-Data retention capabilities of commercial batterybacked static random access memories (SRAMs) exposed to different ionizing dose are investigated. Pattern imprinting is observed for devices exposed to a total dose of 50 kR and above. Room temperature annealing and recovery is also recorded. A model for the pattern imprinting behavior in SRAMs is presented based on the general understanding of defects produced in MOSFETs due to ionizing radiation.

TCAD simulation of radiation-induced leakage current in 1T1C SDRAM

Microelectronics Reliability, 2018

In order to identify the physical mechanism of retention time drop in irradiated SDRAM cell, we implemented the Gossick model of displacement damage cluster into a TCAD simulation tool. Simulation results show that the cluster's position is the key parameter of the phenomenon. Besides that, obtained results are coherent with previous studies and explained by semiconductor physics. Other technological parameters of the cell also influence its response to displacement damage clusters. Leakage current induced by clusters depends exponentially on temperature.

Ionizing Radiation Effects on Non Volatile Read Only Memory Cells

2012

Threshold voltage and drain-source current behaviour of nitride read only memories (NROM) were studied both in situ during irradiation or after irradiation with photons and ions. loss fluctuations are well explained by the same Weibull statistics regardless of the irradiation species and total dose. Results of drain current measurements in-situ during irradiation with photons and ions reveal a step-like increase of with the total irradiation dose. A brief physical explanation is also provided. Index Terms-Flash memories, nitride read-only memories (NROM), oxide/nitride/oxide (ONO), radiation hardness.

Characterization of data retention faults in DRAM devices

2014 IEEE International Symposium on Defect and Fault Tolerance in VLSI and Nanotechnology Systems (DFT), 2014

Dynamic random access memory (DRAM) is the most widely used type of memory in the consumer market today, and it's still widely used for mass memories for space application. Even though accurate tests are performed by vendors to ensure high reliability, DRAM errors continue to be a common source of failures in the field. Recent large-scale studies reported how most of the errors experienced by DRAM subsystem are due to faults repeating on the same memory address but occurring only under specific condition.

A New Direct Evaluation Method to Obtain the Data Retention Time Distribution of DRAM

IEEE Transactions on Electron Devices, 2006

The authors have developed an efficient and accurate method to obtain the data retention time distribution of DRAM from the physics-based device simulation and the numerical integration of the probability space composed of three independent random variables, namely 1) the number, 2) the location, and 3) the energy level of traps, where each trap acts as a localized leakage source. Compared with the recently proposed Monte Carlo method, this method is much more efficient and free from the statistical error in the tail distribution. Furthermore, it can be easily applied to the problem involving a complex geometry and the nonuniform spatial distribution of traps. With this method, the retention time distribution of an 80-nm technology DRAM with the recess-channel-array transistor is studied.

Ion-induced stuck bits in 1T/1C SDRAM cells

IEEE Transactions on Nuclear Science, 2001

Radiation exposure of certain types of devices tends to stick bits, causing them to not be read out correctly after programming. Evidence of a linear trend in stuck bits in SDRAM memory cells is presented. This trend makes a cross section, as traditionally defined for single-event effects, unambiguous. However, there are considerable part-to-part variations in the cross section.

Proton-Induced Single-Event Degradation in SDRAMs

IEEE Transactions on Nuclear Science, 2016

Retention time and cell functionality degradation under proton irradiation is studied for SDRAM references that exhibit in-flight faulty behavior on satellites. Proton irradiation, with an adapted test protocol, allows to reproduce these effects and to gain a valuable insight on this phenomenon. Data acquired allow for a physical interpretation of the degradation, which results of one or more damage clusters created by a single particle.